1-Phenyl-5-pyrazolones with 3-(monosubstituted amino) groups such as anilino and acylamino in the 3-position are well known in the photographic art as magenta dye forming couplers. The 1-phenyl group in these couplers can be substituted with a wide range of groups in different combinations or positions to give materials with desired properties. It is widely recognized that chloro groups are excellent substitutents for the 1-phenyl group, with at least two, or more preferably three, chlorines present. It is also known that at least one, or more preferably two, of these chloro groups be in the ortho position of the phenyl ring in order to improve keeping and improve light absorbance; for examples, see GB U.S. Pat. No. 1,494,777 or U.S. Pat. No. 3,926,631. Typically, 2,4,6-trichlorophenyl is a highly preferred group in the 1-position of a 3-(monosubstituted amino)-5-pyrazolone magenta dye forming coupler.
Known 1-phenyl-3-(substituted amino)-5-pyazolone magenta dye forming couplers suffer from numerous deficiencies in photographic film elements. The light stability of the magenta dye that is formed after processing could be improved on. The magenta dye formed may be too hypsochromic for achieving good color accuracy in some formats and such dyes tend to have more than desired unwanted blue absorbance. In addition, as discussed in, for example, U.S. Pat. No. 5,447,831 and U.S. Pat. No. 5,455,150, magenta dyes formed from 1-phenyl-3-anilino-5-pyrazolones lack density in the 550-580 nm spectral region relative to other classes of magenta dyes used in photographic systems, which can lead to printer compatibility problems where one type of printer may read two different films as identical while another does not. In some cases, the magenta dyes can be prone to form aggregates in the film that are not magenta in hue. This causes hue shifts as a function of exposure. In addition, magenta couplers need to have high activity towards oxidized developer in order to maximize system efficiency.
British Patent Specification 1,173,513 describes the use of 3,4,5-trichloro or 3,4-dichloro substituted 1-phenyl-3-acylamino-5-pyrazolone couplers. However, these couplers are prone to aggregation and to exposure-dependent hue shifts. A 4-chlorophenyl group as a generic 1-substituent has been listed along with numerous other possibilities in U.S. Pat. Nos. 4,268,592, 4,297,440, 4,199,361 and 4,336,325 but no examples of complete coupler compounds having such 1-substituents are mentioned.
U.S. Pat. No. 3,928,044 proposes 1-phenyl-3-(5-alkyloxycarbonylanilino)-5-pyrazolone couplers in which the anilino ring contains an ortho substituent and contains an ester substituent in the meta or para position. The patent is extremely broad as to the substituents that may be employed on the 1-phenyl ring, the common 2,4,6-trichloro phenyl ring being most prominent. The only specific coupler mentioned having a 4-chloro phenyl ring in the 1-position is compound 36 in column 8 of the patent. However, such couplers having the indicated ester and other substituents on the anilino ring result in magenta dyes that are too hypsochromic in terms of .lambda.max when developed in accordance with the conventional Kodak Flexicolor.RTM. C41 process. It appears from the specification that the presence of a substituent in the ortho position of the 1-phenyl group is either preferred or essential. If the coupler contains an ortho chloro group as specified, then the dye would also be too narrow in bandwidth and have insufficient density at 580 nm.
A specific example of a 1-(4-chlorophenyl)-3-anilino-5-pyrazolone coupler is shown as Coupler 19 in U.S. Pat. No. 4,163,670. However, this coupler contains an acylamino substituent on the anilino ring which would again produce a magenta dye that is too hypsochromic in terms of .lambda.max.
Compound (5) of U.S. Pat. No. 4,522,915, is another specific example of a 1-(4-chlorophenyl)-3-acylamino-5-pyrazolone coupler. However, this coupler would produce a dye that is too hypsochromic in terms of .lambda.max and that is unballasted and thus not suitable as an imaging component in a photographic element.
British Patent Specification 1,399,306 describes 1-phenyl-3-anilino-5-pyrazolone couplers having substituted carbamoyl or sulfamoyl groups in the anilino ring but whose 1-phenyl group is limited to a 2,4,6-trichlorophenyl group. Such materials have insufficient light stability and activity towards oxidized developer in addition to having insufficient density at 580 nm.
A problem to be solved is to provide a photographic silver halide emulsion layer which exhibits a desired combination of color reproduction capability and dye light stability.